The present invention relates generally to the production of bent glass sheets and, more particularly, to an improved method of and apparatus for bending glass sheets having specially configurated curvatures.
Bent sheets are commonly used as glazing closures in vehicles such as automobiles and the like. In one commercial production of curved or bent glass sheets in large quantities in a mass production facility, the sheets are supported in a horizontal plane and advanced on externally driven roll-type conveyors in a horizontal path successively through a heating area, a bending area and a heat treating area for annealing or tempering the bent sheets.
The heated glass sheets are advanced from the heating furnace to the bending area and accurately located therein between complemental upper and lower glass shaping press members by the engagement of the leading edges thereof with locating stops positioned in the path of movement of the advancing sheets. When properly oriented, the sheet is engaged along its marginal edge portions by the lower press member and lifted from the conveyor rolls for pressing between the complemental shaping surfaces of the opposed press members. The lower or female press member is generally of a ring-type construction having a shaping rail provided with a surface which engages only the marginal portions of the sheet, the rail being segmented in order to clear the conveyor rolls when moved upwardly therebetween. While these outline, ring-type press members have admirably served the purposes for which they were designed in bending glass sheets of conventional curvatures, they are not completely satisfactory in shaping glass sheets of nonsymmetrical shapes, such as those required for utility as sunroofs in vehicle roof tops or for certain specially configurated windshields, for example. The reason for this is that the sheet tends to drift for slip slightly relative to the nonsymmetrical shaping surface of the lower press ring as it is being lifted thereby, as well as when making contact with the nonsymmetrical shaping surface of the upper press ring. Generally, the sheet tends to slip or creep toward the side or edge having the least pronounced curvature, causing the final curvature imparted to the sheet to deviate somewhat from the intended curvature and resulting in an improperly shaped finished product.